In the acute angle △ ABC, the opposite sides of angles a, B and C are a, B and C respectively. If AB + Ba = 6cosc, then the value of tanctana + tanctanb is______ ．

In the acute angle △ ABC, the opposite sides of angles a, B and C are a, B and C respectively. If AB + Ba = 6cosc, then the value of tanctana + tanctanb is______ ．

∵ AB + Ba = 6cosc, from the cosine theorem, A2 + b2ab = 6 · A2 + B2 − c22ab ∵ A2 + B2 = 3c22, then tanctana + tanctanb = cosasinccosscsina + cosbsinccossinb = sinccosc (cosasina & nbsp; + cosbsinb) = sinccosc · sinbcosa + sinacosbsinasinb = sin2csin

A & # 178; tanb = B & # 178; Tana, C = 60 ° to judge the shape of △ ABC
How to find the edge of a corner

a=2R*sinA,b=2R*sinB,
Substituting the known formula:
4R^2*(sinA)^2*(sinB/cosB)=4R^2*(sinB)^2*(sinA/cosA),
The result is: cosa = CoSb,
∵ A and B are the internal angles of the triangle,
A = ∠ B, and C = 60 °,
∴∠A=∠B=∠C,
Δ ABC is an equilateral triangle

A mathematical cosine theorem in senior two
In the triangle ABC, the opposite sides of angles a, B and C are a, B and C respectively,
It is proved that: (A & sup2; - B & sup2;) / (C & sup2;) = sin (a-b) / (sinc)

Certification:
Right = sin (a-b) △ sinc
=(sinAcosB-cosAsinB)÷sinC
=(acosB-bcosA)÷c
=[a(a^2+c^2-b^2)/(2ac)-b(b^2+c^2-a^2)/(2bc)]÷c
=(a^2+c^2-b^2-b^2-c^2+a^2)/(2c^2)
=（a²－b²）÷（c²）
=Left
It's over

Can't simplify the solution of positive and negative numbers
【1】-（-5）；
【2】-（+2）；
【3】+（-3）；
【4】+（+6）；

+5;-2;-3;+6

To simplify the positive and negative, positive is positive. Negative is positive, and positive and negative are negative. Why negative and positive?
Let's talk about four questions; - (+ 0.78) = - (- 3.14) = + (+ 9 and 1 / 5) = + (- 10.1) = make it clear, give wealth 30 if it's right!

Remember eight words
The same sign is positive, the different sign is negative
Now I can do the problem

Simplification: 0 out of 75

0

【1+3+8*6+4+6*6+3+5+1+8+9+10+96+53+42+83+91+64+4532196+635+6】/8

=566675.5

53 and 1 / 3 × 3 / 5-42 and 2 / 3 × 3 / 8 + 36 and 3 / 4 × 4 / 7

Reduced to false fraction
160/3×3/5-128/3×3/8+147/4×4/7
=32-16+21
=37

5-3 and 1 / 2 x = 1 and 1 / 2

5-3 and 2:1 x = 1 and 2:1 2:10-2:3 = 2:7 x 2:7 x 1

5 x-3 = 4 x + 1

（x-3）/5=（x+1）/4
Multiply both sides by 20
4（x-3）=5（x+1）
4x-12=5x+5
5x-4x=-12-5
x=-17